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dlpc350 - Upload images for pattern sequence mode with RGB interface

Other Parts Discussed in Thread: DLPC350

Dear Sir/Madam,

Hi. By far the only way I used to upload the images for pattern sequence mode is upload from insertion into the firmware and flash it into lightcrafter 4500.

From TI doc, it's mostly mentioned about using flash to upload the images inside embedded 48bit RAM for pattern sequence mode. I noticed it's taken quite a long time, almost 200 - 300 ms. Probably due to the decompression steps. 

Is it possible to upload to 48bit RAM using RGB interface which is 120 frames/s? That would be 8.3ms per 24bit images.

Am I possible to upload the image to second 24bit buffer, while triggering the projection of images from another 24bit buffer with pattern sequence mode?

Thanks.

  • Hi Sean,

    The second 24 bit buffer does get loaded while the 1st is being displayed (assuming it has already been loaded). If you are displaying more than 48 1-bit planes, then you will have to take into account the longest image load time from flash when calculating your maximum pattern rate.

    If you are streaming patterns into the device, please reference "Table 4-1. Allowable Pattern Combinations" in the LightCrafter4500 user's guide for more details.

    Thanks,
    Clinton
  • Hi Clinton,

    Thanks for the reply. Please allow me to simplify the questions in a more direct way.
    Am I able to load images using RGB interface for pattern sequence mode instead of using flash?
    Does dlpc350 chipset support that kind of loading methods?

    If it works, I will make a customize a electronic board with dlpc350 for this purposes.
  • Hi Sean,

    Yes, that is possible. Do you have a LightCrafter4500 EVM? You can try this method out if you do.

    Thanks,

    Clinton

  • Hi Clinton,

    Yes, I have LightCrafter 4500 EVM. Could I simulate this using LightCrafter4500 control software?
  • Hi Clinton,

    Additional one more question: Using RGB interface could upload image with native resolution which is 912 x 1140?
    Thanks.
  • Sean,

    The RGB interface can upload an image in the native DMD resolution. In many cases, the images should be exactly 912x1140. Are you looking to upload images which are larger or smaller than that resolution?

    Thanks,
    Paul
  • Hi Paul,

    No, I'm going to upload exactly 912x1140 to have 1 to 1 mapping. So this basically answer my first question, thanks for that.

    2nd question, can I upload images through RGB interface to 2nd buffer while pattern sequence mode is projecting first buffer images.
    For example there will be 3 8bit images on buffer one, which will took 25ms (8.3ms x 3) for the total projection time. It seems for me there's a sufficient time to load to 2nd buffer while it is projecting the first one.

    Can you elaborate more on the timing here?
  • Hi Sean,

    2nd question -
    Pattern exposure - 8.3ms + .230ms (if you have selected the Clear DMD after exposure)

    for three patterns 8.530*3 = 25.59ms

    so basically you must send the Video at the RGB interface <= 39Hz.

    Just configure your source generator at 39Hz; with this you will fill both buffers ~51ms time duration.

    Since you are sending data realtime you can simply keep the video feed active [1st 24-bit] [2nd 24-bit] [1st 24-bit] [2nd 24-bit] , basically alternate b/w two frame buffers.

    Regards,
    Sanjeev
  • Hi Sanjeev,

    Thanks.
    Just to make myself clear: If I'm using 7 bit, it would be 14.19ms for 3 patterns. Which implies 70Hz - 120Hz of RGB interface would be still sufficient to real time load the images for pattern sequence mode.
  • 14.19ms = 70.47Hz;

    You can run maximum 70Hz at the RGB interface, so it is no 70Hz - 120Hz, it is <= 70Hz.

    Regards,
    Sanjeev
  • Hi Sanjeev,

    I don't get it. 

    The projection of 3 pattern took 14.19ms.

    In order to match this speed in loading time, it should be <= 14.19ms.

    Now u are telling me the RGB interface suppose to be >= 14.19ms.

    For example I chose 30Hz (<70Hz). So the time took to load will be 33.33ms.

    So after project 3 images, it will still wait for 19.14ms (33.33 - 14.19) before it able to project the next 3 images. 

    Please correct me if I'm wrong.

  • >> Now u are telling me the RGB interface suppose to be >= 14.19ms.

    Think this way, video frame period must be >= your selected total pattern(s) display period; if you are video frame period is <14.19ms basically the controller will not have enough time to display all the patterns, so in streaming mode, you must make sure that the total pattern(s) period within the video pattern period.

    Back to your example - 

    @ 30Hz, 33.33-14.19 = 19.14ms, the 19.14ms is at the end of the displaying all the three patterns, so you don't need to wait, the trigger o/p appear immediately at the VSYNC

    Regards,
    sanjeev

  • Sorry for interrupting this thread!
    Can you help me with the similar problem?
    How can I obtain one trig_out pulse corresponding with one pattern streaming from RGB interface? Like this dlp_nirscan -l40 -E250 -S960?
    It is described in
    e2e.ti.com/.../575990

    Thank you!